Self-Healing Plastic Changes Color When Damaged

A new type of thermoplastic can heal itself when exposed to light, temperature changes, or changes in pH, after first turning red to show that it's been damaged. The research was presented at a press conference at the 2012 National Meeting and Exposition of the American Chemical Society.

Marek W. Urban, professor at the University of Southern Mississippi, who led the research team that has made the discovery and reported its findings, said that the new co-polymer mimics the human skin’s ability to heal scratches and cuts, and could offer the ability of self-repairing surfaces to cellphones, laptops, and cars.

A new type of plastic that mimics human skin changes color first to show damage from cuts and scratches, then heals itself when exposed to light or changes in temperature or pH.
(Source: Professor Marek W. Urban, University of Mississippi)

Plastics can be difficult or impossible to repair once they've been scratched or cracked, yet they are now prevalent in many different products. The search for self-healing plastics has become more urgent as plastics have become ubiquitous in critical structures such as automobiles and aircraft, since damage can change a plastic's electrical, acoustical, and thermal characteristics.

Many types of self-repairing plastics mimic the abilities of biological systems. One method implants capsules into a plastic. When the plastic is scratched or cut, the capsules break open and release repair compounds that fix the damage. Another method depends on plastics that repair themselves by responding to specific outside stimuli, such as heat, light, or chemical agents.

While self-repairing plastics that depend on embedded healing compounds can only repair themselves once, Urban's plastic can repair itself many times. The process for producing the plastic is also water-based, making it more environmentally friendly and less expensive.

Other approaches include smart coatings, paint, or adhesives. These can be applied to the material and reveal damage when viewed at certain wavelengths, or signal damage by changes in electric current.

William, thanks for your comment. I agree with you about this not being likely for consumer-grade use. We addressed this issue earlier in the thread: since this is not close to commercial development yet, price and cost differentials are unknown. But self-healing plastics like this one--which unusually can self-heal multiple times--multiply the life of the object several times. Less plastic gets used during that time, so the COO to manufacturers would be lower than buying it once. It's not aimed at high-volume, low-cost throwaway applications, but ones where continued use of a high-value product is important, such as military or medical products.

It would be quite useful to know some of the more common materials propertiies of this self healing material, such as strength, stiffness, and temperature ratings, and that all important property, PRICE. My guess is that it would never be found in consumer goods evenif the cost were half that of styrene regrind. It appears that many consumer goods have avery intentional low quality level, so that they would be replaced every few months.

ChasChas, thanks for that comment. I agree with you. I've reported on several other experimental materials that seem to be moving toward intelligence, some of them via nanotechnology, and many of them based on shifts in electrical charge.

Nadine, thanks for the clarification. Since this material is aimed at self-repairing surface damage, I don't think it's designed for implants. But that's an interesting idea. There are many biocompatible plastics made for that application, and designing one of those to be self-healing would be a good PhD project.

Ann: I'm thinkiing specifically about joint replacement. I had the honor to attend an orthopaedic surgeons conference a few months ago. The technology is very interesting and has been making slow advances, especially in hip replacements. Even temperature and PH changes would be problematic for spine, knee and hip replacements.

Mydesign, most countries are trying to find alternate feedstocks for plastics, like bioplastics, and/or design plastics that are compostable or recyclable, as I've written about here

http://www.designnews.com/author.asp?section_id=1392&doc_id=239645

http://www.designnews.com/document.asp?doc_id=239662

http://www.designnews.com/author.asp?section_id=1392&doc_id=240409

http://www.designnews.com/author.asp?section_id=1392&doc_id=241854

http://www.designnews.com/author.asp?section_id=1392&doc_id=242634

Meanwhile, these new plastics are only a drop in the huge bucket of the amount of plastics we consume. So extending the life of non-recyclable, non-compostable plastics by reusing them helps keep them out of the landfill.

Nadine, intense light is one possible exposure mechanism--the article also mentions changes in temperature or pH. I'm not sure why strong light would be a problem for an implant, since an implant is usually kept away from light. Can you tell us more about what you mean?

Many of the new adhesives we're featuring in this slideshow are for use in automotive and other transportation applications. The rest of these new products are for a wide variety of applications including aviation, aerospace, electrical motors, electronics, industrial, and semiconductors.

A Columbia University team working on molecular-scale nano-robots with moving parts has run into wear-and-tear issues. They've become the first team to observe in detail and quantify this process, and are devising coping strategies by observing how living cells prevent aging.

Many of the new materials on display at MD&M West were developed to be strong, tough replacements for metal parts in different kinds of medical equipment: IV poles, connectors for medical devices, medical device trays, and torque-applying instruments for orthopedic surgery. Others are made for close contact with patients.

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